This invention relates to an immunoassay which measures the concentration of cyclosporin analytes in sample fluids.
Cyclosporins (i.e. cyclosporins A, B, C and D) are 11 amino acid residue cyclic peptides which were discovered during the search for new antifungal compounds. Although initially proposed to be antibiotic, antiarthritic and antiinflammatory compounds, their actions as immunosuppressives have come to outweigh all other uses. This is especially so in the case of cyclosporin A. This compound has had an enormous impact upon the continuation of research on human tissue transplantation leading some to suggest that tissue typing and matching are no longer needed for cyclosporin recipients.
Patients receiving cyclosporin A alone or in conjunction with prednisone therapy, subsequent to tissue transplantation, show a lower incidence of tissue rejection, lower incidence of infection, higher graft survival rates, and greater long-term survival rates, when compared to conventional therapeutic protocols. However, the clinical use of cyclosporin A is complicated by the narrow therapeutic window that exists between the inadequate immunosuppression that occurs at low doses and the adverse effects of hepatotoxicity, nephrotoxicity and sepsis resulting from overadministration.
The only way that cyclosporin A can be efficaciously administered is by periodic monitoring of plasma drug concentrations. For this to be accomplished, an easy assay for determining cyclosporin A levels needs to be developed. An easy assay for cyclosporins B, C and D would also be useful insofar as such compounds find clinical acceptance similar to that of cyclosporin A.
Currently, two types of assays are available for measuring patient drug levels: high-performance liquid chromatography and radioimmunoassay using a 3H-cyclosporin tracer. Both the HPLC assay and the tritiated assay are time consuming for personnel, expensive to perform, and generally too slow in providing data. Thus, there is a need for radioiodine immunoassay and fluorescence immunoassay of cyclosporins.